Motor mounting



Y Feb. 15, 1938. E M E 2,108,515

MOTOR MOUNT ING Filed Oct. 22, 1928 4 Sheets-Sheet 1 Feb. 15, 1938. c,SUMMERS 2,108,515

4 MOTOR MOUNTING Filed Oct. 22, 1928. 4 Sheets-Sheet 2 gnue'ntoz Feb.15, 1938. SUMMERS Y 2,108,515

MOTOR MOUNT ING Filed Oct. 22, 1928 4 Sheets-Sheet 3 Patented 1a. 1.5,1938 UNITED STATES MOTOR MOUNTING Caleb E. Summers, Pontiac, Mich,assignor, by

mesne assignments, to General Motors Corporation, Detroit, Mich, acorporation of Delaware Application October 22, 1928, Serial No. 314,203

. 17 Claims.

This invention has to, do with mountings for engines and similarmachines, the object being to prevent transmission to the supports or tothe operator of the vibrations inherent in the engine during operation.The invention has particular application to engines usedin automobiles.

Myimproved mounting is especially applicable to engines which aresubject to lateral vibration or vibration about an axis extendinglongitudinally thereof. It is so designed as to permit the motor tofreely perform its vibratory movement rather than to attempt to confineit in one position as in the conventional mounting. In addition, ifdesired, means may be provided for bracing the motor against chancevibration, this means being so designed that engine vibration is nottransmitted through it to the frame or other part of the car to which itis secured. The engine controls are also preferably so designed thatnone of the engine vibration will be transmitted through them to theoperator.

The underlying principles embodied in this invention can best beexplained in the course of the following description of a specificapplication of it.

I have disclosed my improved mounting applied to an eight cylinderautomobile engine of herein described is mounted in a conventionalchassis, its inherent vibration takes the form of an oscillation of themotor about a neutral axis extending longitudinally of the engine andinclining upwardly from apoint at the rear of the engine. I have sodesigned my motor supports as to .permit the engine to oscillate withsubstantial freedom about thisaxis In other words, instead of rigidlytying the engine down to the frame, with or without the interposition ofrubber blocks, or

springs, as is now common practice, I have provided a mountingpermitting the engine to oscillate with more or less freedom in responseto its inherent vibration. The result is the elimination of the minutebut objectionable thrusts and tugs at the frame which would otherwise beproduced by the vibration. This type of mounting is, however, subject tothe objection thatthe engine will tend to swing as a result of externalforces, such as rolling and tossing of the car as a consequence ofinequalities in the road, travelling around curves, and the like. Toovercome this tendency I have equipped my engine with special bracingmeans designed to resist this movement without, however, interferingwith the free oscillation of the engine in response to engine vibration.The bracing means extends from the engine to some fixed part of thevehicle, such as the frame or body, and to avoid the transmission offorces from the engine tothe frame or body through these parts, eitherof the following arrangements may be employed:

Where, as in the case of the engine referred to, the vibration is offixed amplitude and its frequency varies with the engine speed, thebracing means may be so designed as to, in effect, automaticallyincrease and decrease in length in synchronism with the enginevibrations; that is, as the engine moves away from the point ofconnection of the bracing means to the frame the over-all length of thebracing means is automatically increased, and as the engine moves towardthe point of connection of the bracing means to the frame, the over-alllength of the bracing means is decreased. Owing to this mode ofconnection the bracing means is at no time subject to any appreciabletension or compression, so that no force is transmitted through it tothe frame as a consequence of engine vibration, but it nevertheless isat all times effective to resist any tendency of the engine to move inresponse to extraneous causes, such as swaying or pitching of thevehicle. The automatic adjustment of the bracing means is bestaccomplished by the engine since it must be in synchronism with thevibration inherent in the operation of the engine. The preferredembodiment of bracing means consists essentially of a brace member whoseeffective point of connection with the engine is varied in synchronismwith the engine vibration by means of suitable mechanical devices suchas a cam and lever, the cam being rotated by the engine.

Another form of bracing means, which I like wise have embodied in mypreferred motor mounting, consists of a simple strut or brace connectedto the engine at a point lying within or very close to the axis ofoscillation of the engine, in which case the movement of the engine isalong an arc of such small length that it is negligible and the strutmay be rigidly connected both to the engine and frame without beingsub-' ject to appreciable tension or compression as a result of enginevibration. As a consequence no vibrations are transmitted through it'.

Not only is it desirable to prevent transmission of --engine vibrationsto the frame and body, but it is also desirable to prevent transmissionof vibration to the driver through such controls as are connected withthe engine at points sufiiciently far from the axis of vibration as tohave appreciable movement. The clutch pedal usually falls within thisdescription. To accomplish the desired result the connections betweenthe pedal and the engine are so designed as to permit free movement ofthe engine, without, however, transmitting this movement to the pedal.

In the drawings:

Figure 1 is a longitudinal sectional view through an automobile chassisshowing an engine mounted therein in accordance with my invention.

Figure 2 is a fragmentary top plan view of the construction shown inFigure 1.

Figure 3 is a view of part of the clutchoperating connections taken online 3-3 of Figure 1.

Figure 4 is a front elevation of the engine with parts broken away toshow the bracing means. 7

Figure 5 is a top plan view of Figure 4 broken away to show the bracingmeans and also the method of attachment of the front engine support.

Figure 6 is ure 2.

Figure 7 is a section on line 1-1 of Figure 6.

Figure 8 is a perspective view showing-modified forms of front and rearmotor mounting.

Figure 9 is a sectional view through the front motor mounting andadjustable bracing means shown in-Figure 8.

Figure 10 is a view of the construction of Figure 9 looking from theleft' side of that figure.

Figure 11 is a section through the rear motor mounting of Figure 8.

The form of the invention shown in Figures 1 to '7 will first bedescribed. I have shown in these figures an 8-cylinder internalcombustion engine of the V type. One bank of 4 cylinders is indicated atI0 and the other bank'is indicated at l2. The angle between the banks ispreferably 90. I have indicated in dotted lines in Figure 1, thecrankshaft H to which the pistons operating in the cylinders areconnected by means of the usual connecting rods, not shown. The shaftillustrated is of the common type having the four throws in one plane,the connecting rods of opposing cylinders being connected to commonthrows. The engine as so far described is conventional: audit ispreferably operated with the usual firing order, 1, 3, 4, 2, for each ofthe banks of cylinders. The ing is, of course, alternated between thebanks of cylinders so that if the cylinders of bank Id be numbered 1,3,5 and 7, and the cylinders of bank I! be numbered 2, 4, 6 and 8, theactual firing order is 1, 8, 5, 4, '7, 2, 3, 6. The firing order chosenis likewise conventional. t

It has long been known that engines of the type illustrated arecharacterized by an inherent lateral vibration when the engine is inoperation. I have found after-careful investigation that this lateralvibration is in fact an oscillation about a neutral axis extendinglongitudinally of the motor. The specific engine illustrated is of theconventional unit power plant type' in which the flywheel housing It isrigidly secured to the engine block, and to the flywheel housing issecured the transmission housing l8. These parts are then mounted as aunit on the chassis frame 20. I have found after careful experimentswith a view taken on line 6-6 of Fig- V-8 engines of the unit powerplant type such as shown on the drawings that owing to the distributionof masses the engine assembly tends to oscillate about a neutral axisextending centrally of the engine and inclining upwardly from a point inthe vicinity of the universal joint 22 to a point above the engine.

The axis of oscillation is indicated by line XX of Figure 1. Thisvibration, or oscillation, as is well known, is produced by unbalancedinertia forces resulting from motion of the reciprocating parts such asthe pistons and connecting rods, and also by gas torque reaction andother factors.

The vibration is characterized by a fixed amplitude, and its frequencyvaries directly with the engine speed. The amplitude of the vibration issmall being usually not more than a few thousandths of an inch frommid-position. However, with present day engine speeds, it is verynoticeable and is decidedly objectionable to the occupants of the car.Knowing the character of vibration performed by the engine the problemhas been to so mount the engine as to prevent the transmission of thevibration to the chassis.

I have solved this problem by mounting the engine so as to permit it tohave substantial freedom of movement with the result that the frame isnot subject to the thrusting and tugging that ensues where the engine isrigidly clamped to the frame. Since the rear end of the power plant isvery close to the axis of oscillation XX, the amplitude of theoscillatory movement will be very slight so that a simple type ofsupport may be used. I have illustrated this support at 24 and it isshown in detail in Figure 7. The support consists of a bracket 26supported on the cross frame member 28, and carrying a stud 30 whichpasses through aligned perforations in a rubber cup 32, metal cup 34 andbracket 36 bolted to the rear end of the transmission housing l8. Uponthe upper end of the stud 30 is threaded the vnut 38 for holding theparts assembled. It will be noted that the rubber cup 32 is providedwith an annular extension 40 projecting into recess formed in theunderside of the bracket 34 and that the aperture in the bracket 34through which the stud 30 passes is of larger diameter than the stud 30.with this arrangement the extension 40 as well as the cup-shaped designof the rubber member 32 yieldingly permit the engine to have a slightfreedom of movement in all directions. As previously pointed out sincethe support is very close to the axis X-X, this limited amount offreedom of movement is suflicient to take care of the engine vibration.

The vibration of the forward part of the engine is of considerableamplitude since it is quite a bit removed from the axis of oscillation.The supports for the front end must therefore be designed to permit ofconsiderable movement. The front motor mounting is best shown in Figures4 and 5, and consists of brackets 42 bolted to the sides of the motorblock and suspended from brackets 44 secured to the chassis side framemembers, by means of links '46. The brackets 44 mayconsist of U-shapedmembers 41 and 48 secured back to back and to the side channel members50 by means of bolts 52. The links 46 may be of the type commonly usedfor spring shackles.

I have indicated at X 'on Figure 4 a point on the axis XX of Figure 1.The links 46 are preferably so arranged as to normally lie along radiidrawn from said point and indicated by the lines XY of Figure 4. Thearrangement of links as shown permits the engine freedom to oscillateback and forth along a path which is practically indistinguishable froman are drawn about axis XX as a center;

With the engine mounted in the manner described there is nothing toprevent its oscillation in response to extraneous forces such'as rollingor tossing of the car in its movement over rough roads and aroundcurves. This, of course, is undesirable and I shall now describe themeans for preventing such chance movement of the engine. The principleinvolvedin my preferred form of bracing means consists in designing thebrace so that it is self-adjusting to take care of changes in positionsof the engine in response to its inherent vibration but positivelyresists chance movement. The bracing means is best shown in Figures 4and 5, and comprises a bracket 54 bolted to the side frame member 58.From the bracket projects a strut 56 in the form of a bolt having aheaded end 58. The strut is adjustably secured to the bracket by meansof lock nuts 68. Within an extension 62 of the engine housing is formeda chamber 63,.the outer end of which is closed by cover plate 64. Withinthe chamber is a cam follower in the form of a lever 65 pivoted at 66 tothe engine block. The lever is provided with a notch 68 within which isreceived head 58 of the bolt 56. A coil spring 61 surrounds the stem ofthe bolt, bearing at one end against the head 58 and at the other endagainst a plate 18 bolted to the extension 62 of the engine block.Suitable packing is provided about the strut 56 as shown at I2 toprevent the escape of oil. The upper end of the lever 65 is providedwith a nose bearing against a four lobed cam I4 mounted on the usualcamshaft 16 driven from the engine crankshaft in the customary manner.

. The parts of the bracing means are assembled with the spring 61 undercompression so as to hold the cam follower 65 against the cam 14. Theother end of the strut 56 is then rigidly clamped to the bracket 54. Thestrut 56 is cons equently fixed in position and the efiect of rotationof the cam 14 is simply to hold the follower 65 against the headof thestrut in all positions which the enginevassumes in the ,course-of itsvibration. As a consequence, the parts of the I bracing means, that is,the strut 56, the cam the effect of this would be to move the member outof contact with the head of the strut 56. As a result the strut would beineffective to brace the engine. -,To avoid this the member 65 is mademovable and the cam I4 is so designed that at the same time the engineis moving to the right the cam follower 65 is riding up toward a highpoint on the cam causing the follower to swing to the left and maintainconstant engagement with the head of the strutthroughout the swing. Thereverse operation takes place when the motor swings to the left.

The vibration to which this type of engine is subject is of twicecrankshaft frequency so that I where the cam is mounted on the camshaftwhich is driven at half crankshaft speed, it is necessary to provide itwith four lobes to synchronize. the

movement of the bracing means and the engine oscillations. Obviously,the cam if mounted on the crankshaft would require but two lobes.

I have preferred to employ an additional bracing means in the form of abar I8 bolted at one end 88 to a frame member or other fixed part of thechassis and at the other end 82 to a part of the engine lyingsubstantially in the axis X-X. The amplitude of oscillation of theengine adjacent the point of connection 82-is very small so that a rigidbrace may be employed without apportions of the engine. remote from theaxis.

In Figures 8 to 11, I have shown a somewhatmodified form of mounting.The motor here indicated at I88 is of the same type as that previouslydescribed. The adjustable bracing means is likewise of substantially thesame design and is indicated by the same reference characters. In thisform of the invention the front motor supports instead of being in theform of links take the form of flexible straps I82 hung from bracketsI84 bolted tothe chassis side frame members I86. To the lower end of thestraps I82 are secured brackets I88 bolted to the engine block. As inthe case of the links 46 of Fig.4, the straps I82 normally extend in aradial direction from the axis XX. The straps may be made of'metalpreciably interfering with the free swinging of or fabric, or acombination of the two, the requisite being that they be flexible topermit the lateral vibration of the engine previously described. If offabric they may be made in as many plies or layers as desired, and maybe impregnated with rubber or the like.

Obviously, in this form of the invention the front motor suspensionoperates in exactly the same way as in the form first described.

The rear motor support is "shown in Figures 8 and 11 and consists ofbrackets I I8 secured to the channel side frame members I86. The rearend of the motor is provided with arms II2 which overlie the brackets H8and are secured there- ,to. Between the brackets and the arms areinterposed stiif coil springs II4 housed in recesses in secured to thebrackets 8. These springs bear most of the weight of the rear end of themotor. Bolts II8 project through aligned openings in the arms H2 and thebrackets II8. Encircling the bolts I I8 and positioned directly aboveand belowthe arms II8 are resilient cushions I28 housed between metaldiscs I 22. The resilient cushions I28 consist of alternate layers ofrubber and fabric. The assembly isheld in place by means of the nut I24threaded on the lower end of bolt H8. The resilient cushions I28 absorbminor shocks and vibrations too small to be appreciably cushioned by thesprings II4.

It is obvious that any connection between the motor and frame will serveto transmit vibrations to the frame unless designed to avoid thisresult,

as in the ways pointed out in this application. I

It is also obvious that vibration will likewise be transmitted throughany controls which lead from the motor to the operator. It is henceundesirable to mount the controls upon the motor. In some cases, as inthe case of the clutch pedal, it is not possible to avoid a connectionwith the motor since the clutch itself is housed within. the

unit power plant. To avoid the transmission of 1 engine vibrations tothe clutch pedal, I have developed a special design of clutch pedallinkage as shown in Figures 1 and 2. I28 indicates the lever whichengages the clutch operating yoke, not shown. This lever customarilyswings about 'a vertical axis. The clutch pedal is indicated at I22 andis mounted on a rock shaft I24 carried by bracket I26 bolted to thecross frame member projecting from the lower end of the clutch pedalwould be connected with the lever I28 by means mounting designedespecially for V-8 engines. I-

of a horizontally extending link but with this construction the lateralvibration of the motor.

carrying, with it the arm I20 and link I34 would produce a backward andforward oscillation of the clutch pedal I22. Since the parts I20 and I34oscillate about the axis XX as a center they move slightly fore and aftas well as up and down. With the horizontally extending link the entirefore and aft component of the vibration of the engine is available tooscillate the clutch pedal. To avoid this difficulty I have so arrangedthe clutch operating lever I20 and the arm I32 that the link I34connecting them will extend in a direction parallel to the axis X-X. Ihave likewise provided a swinging connection between the link I34 andthe arm I32. With'this construction the inherent oscillation of themotor will carry the lever I20 and link I34 with it causing the latterto rock in the joint provided in the arm I32 without producing anyappreciable oscillation of the pedal I22. I have found that upon actualtest that this arrangement entirely prevents transmission of enginevibrations to the driver through the clutch pedal.

I have disclosed in this application a motor mounting are applicable toother types of engines possessing similar vibrations and also to othermachines subject to the same difllculty. I

have in mind, specifically, pumps and compressors such as commonly usedin household refrigerators, electric motors and the like as beingdevices to which my improved mounting may be applied. It is my intentionto cover the various uses of this mounting in ,this patent application.

.The special clutch pedal mounting is applicable to all kinds of.engines whatever be the character of the vibration as the linkages mayalways be designed in accordance with the principleshere outlined so asto make it impossible for the engine vibrations to reach the operator.

It is to be understood that the references in this application to frontand rear of the engine, to downward inclination of axes, etc., are to beconstrued in a relative sense and not in an absolute sense, since inother arrangements of the engine and its support the parts may haveother positions but may function in identical fashion.

In the interests of brevity the term chance vibration is employed todesignate vibration or shifting of the motor other than the inherent 1.An engine or the like of the type that is subject to oscillation about alongitudinal axis under the action of forces inherent in its operation,a support, means for mounting the engine on the support so as to permitit to have substantially free oscillatory movement about said axis inresponse to said forces, bracing means for the engine to resist chancevibration, and means operated by the engine for adjusting said bracingmeans.

2. An engine or the like of the type that is subject to oscillationabout a longitudinal axis under the action of forces inherent in itsoperation, a support, means for mounting the engine on the support so asto permit it to have substantially free oscillatory movement about saidaxis in response to said forces, a strut connected to the supportandengaging the engine and adapted to resist chance vibration of theengine, and means operated by the engine for adjusting the point ofcontact of said strut and the engine.

3. An engine or the like of the type that is subject to. oscillationabout a longitudinal axis under the action of forces inherent in itsoperation, a support, means for mounting the engine on the support so asto permit it to have substantially free oscillatory movement about saidaxis in response to said forces, and bracing means for the engineadapted to resist chance vibration thereof, including a strut secured tothe frame, a lever engaging the strut, and means driven by the enginefor adjusting the position of the lever.

4. An engine or the like of the type that is subject to oscillationabout a longitudinal axis under the action of forces inherent in itsoperation, a support, means for mounting the engine on the support so asto permit it to have substantially free oscillatory movement about saidaxis in response to said forces, and bracing means for the engineadapted to resist chance vibration thereof, including a strut secured tothe frame, a lever pivoted to the engine, a cam driven by the engine andengaging the free end of the lever, said lever being in bracing contactwith said strut at an intermediate point.

5. The combination with an automobile chassis frame and an internalcombustion engine assembly with pistons and cranks so arranged thatunbalanced forces are produced by the operation of the engine tending tocause vibrations of the engine about a longitudinal axis and with themass of the assembly so distributed relatively to the point ofapplication of the forces as to cause said axis to be inclineddownwardly from front to rear, of means connecting said assembly to saidframe comprising supporting means at the front of the engine adapted topermit substantially free oscillation of the engine assembly about saidaxis and additional supporting means at the rear of the engine assemblylocated in close proximity to said axis.

6. An engine or the like of the type that is subject to inherentoscillatory vibration about an axis inclining downwardly from a pointadjacent the front of the engine, a support for the rear of the enginelying adjacent said axis, and supporting means for the front of theengine designed to permit said inherent oscillatory vibration, and meansfor resisting chance vibration of the engine.

7. In an automobile, in combination, a chassis frame, an engine in thechassis frame arranged to propel the automobile, said engine beingsubject to inherent oscillatory vibration about an axis incliningdownwardly from a point adjacent the front of the chassis under theaction of forces inherent in its operation, supports for the enginemounted on the chassis and designed to permit said inherent oscillatory.vibration, and independent means for limiting the amplitude of movementof the engine.

. 8. An engine or the likehaving a drive shaft, said engine being of thetype that is subject to oscillation about an axis non-coincident withthe axis of the drive shaft under the action of forces 7 inherent in itsoperation, a support, and means for mounting the engine on the supportarranged to permit the engine to have substantially free oscillatorymovement about said axis in response to said forces, and independentmeans for restraining the movement of the engine without interferingsubstantially with said oscillation.

9. In an automobile the combination of a chassis including wheel drivingmeans, an engine in the chassis comprising a crankshaft, .cylinders,pistons in the cylinders arranged to drive the crankshaft, a connectionbetween one end of said crankshaft and the Wheel driving means, saidengine being subject to oscillation about a longitudinal axisnon-coincident with the axis of said crankshaft under the action offorces inherent in the operation of the engine, and means for mountingthe engine in the chassis arranged to permit the engine to havesubstantially free oscillatory movement about said longitudinal axis inresponse to said forces, and independent means connecting said engineand chassis for restraining the movement of said engine.

10. In an automobile the combination of a chassis having a propellershaft, an engine in the chassis comprising a crankshaft, cylinders,pistons in the cylinders connected to drivethe crankshaft, atransmission unit rigidly mounted on said engine and operativelyconnected at one end with said crankshaft and at the other end with thepropeller shaft, said engine and transmission being subject tooscillation about a longitudinal axis non-coincident with the axis ofsaid crankshaft under the action of forces inherent in the operation ofthe engine, and means for mounting the engine and transmission'in thechassis arranged to permit the engine to have substantially freeoscillatory movement about said longitudinal axis in response tosaidforces, and independent means connecting said engine and chassis forrestraining the movement of said engine.

11. The combination with a motor vehicle frame and an engine unit whichhas a tendency to oscillatory movement during operation, of two spacednon-metallic and yiel'dable mountings supported by the frame upon whichthe engine unit is mounted, said mountings .adapted to yield slightly tosuch tendency to oscillatory movement of the engine unit with respect tothe frame under the impulses of the engine unit when in operation, theaxes of the engine crank shaft and of the oscillatory movement of theengine unit intersecting at one end of the unit and a stabilizingconnection between the engine unit and the frame.

12. 'Ihecombination with a unit power plant including an internalcombustion engine having a crankshaft and a power transmission mechanismat one end adapted for connection with universal joint drive means and asupport, of resilient connections between the support and power plantarranged near opposite ends of the power plant and constructed toaccommodate power plant oscillation due to engine operation reactionsabout an axis inclined to the axis of the engine crankshaft andintersecting the same at the end adjacent said transmission mechanism,said connections imposing no substantial restriction on oscillation ofthe power plant such as would cause the oscillation to manifest itselfin objectionable thrusts and tugs at the frame.

13. The combination of an engine or the like having a drive shaft andhaving its masses so disposed that it is subject to oscillation about a.longitudinal neutral axis extending at an angle to the drive shaftunder the action of forces inherent in its operation, a, supportingframe, and means for mounting the engine on the frame for oscillationabout said axis so as to offer substantially no resistance to suchoscillation and prevent the oscillation frommanifesting itself inobjectionable thrusts and tugs at the frame.

14. In an automobile or the like the combination of an engine having adrive shaft, a propeller shaft, means connecting the propeller shaft tothe rear end of the drive shaft, said engine having its masses sodisposed that it is subject to oscillation about a neutral axis inclineddownwardly from front to rear and intersecting the drive shaft axisadjacent its connection with the propeller shaft under the action offorces inherent in the operation of the engine, a supporting frame, andmeans for mounting the engine on the frame for substantiallyunrestrained pivotal movement about said axis, thereby preventing theoscillation from manifesting itself in objectionable thrusts and tugs atthe frame.

15. In an automobile or the like the combination ofan engine having adrive shaft, a propeller shaft, means connecting the propeller shaft tothe rear end of the drive shaft, said engine having its masses sodisposed that it is subject to oscillation about a neutral axis inclineddownwardly from front to rear and intersecting the drive shaft axisadjacent its connection with the propeller shaft under the action offorces inherent in the operation of the engine, a supporting frame, andmeans spaced along said axis mountirig the engine on the frame forpivotal movement about said axis, thereby preventing the oscillationfrom manifesting itself in objectionable thrusts and tugs at the frame,one of said mountings being located adjacent the connection of thepropeller shaft to the drive shaft.

16. In an automobile or the like the combination of anengine having adrive shaft, 2. propeller shaft, means connecting the propeller shaft tothe rear end of the drive shaft, said engine having its masses sodisposed that it is subject to oscillation about a neutral axis inclineddownwardly from front to rear'with respect to the drive shaft under theaction of forces inherent in the operation of the engine, a supportingframe,

and yieldable means mounting the engine on the frame for yieldinglycushioned pivotal movement about said axis, thereby preventing theoscillation from manifesting itself in objectionable thrusts and tugs atthe frame.

17. In an automobile or the like the combination of a unit power plantincluding an engine having a drive shaft and a transmission connected tothe rear thereof, said engine and transmission being secured together asa unit, a propeller shaft connected to the drive shaft through, saidtransmission, said power plant having its masses so disposed that it issubject to oscillation about a neutral longitudinal axis inclineddownwardly from a point above the drive shaft at the front thereof underthe action of forces inherent in the operation of the power plant, asupporting frame, and means for mounting the power plant on the frame,said means being so oriented with respect to said axis as to conditionthe power plant for substantially unrestrained oscillation about saidaxis so as to prevent the power plant from thrusting and tugging at theframe.

CALEB E. SUMMERS.

